Turbo compressor and refrigeration cycle device having turbo compressor

This application is the National Stage filing under 35 U.S.C. 371 of International Application No. PCT/KR2021/008372, filed on Jul. 1, 2021, which claims the benefit of the earlier filing date of and rights of priority to Korean Application 10-2021-0075066 filed on Jun. 9, 2021, the contents of which are all hereby incorporated by reference herein in their entirety.

A turbo compressor and a refrigeration cycle device having a turbo compressor are disclosed herein.

Generally, compressors are largely divided into positive displacement compressors and turbo compressors. A positive displacement compressor is a system that draws in, compresses, and discharges a fluid using a piston or a vane, as in a reciprocating or rotary compressor. On the other hand, a turbo compressor is a system that draws in, compresses, and discharges a fluid using a rotational element.

The positive displacement compressor determines a compression ratio by properly adjusting a ratio between intake volume and discharge volume, in order to obtain a desired discharge pressure. Accordingly, the positive displacement compressor has constraints in making the overall size of the compressor smaller in comparison to capacity.

The turbo compressor is similar to a turbo blower, but has a higher discharge pressure and a lower flow rate than the turbo blower. The turbo compressor increases the pressure on a continuously flowing fluid, and may be classified as an axial compressor when the fluid flows in an axial direction or a centrifugal compressor when the fluid flows in a radial direction.

Unlike positive displacement compressors, such as reciprocating compressors or rotary compressors, it is difficult to obtain a high pressure ratio as desired by compressing a fluid only once, due to various factors, such as processability, mass productivity, and durability, even if a shape of blades of a rotating impeller is optimally designed. In this regard, there is a well-known multi-stage turbo compressor which has a plurality of impellers in the axial direction and compresses a fluid in multiple stages.

The multi-stage turbo compressor compresses a fluid in multiple stages using a plurality of impellers mounted to a rotary shaft on one side of a rotor or by a plurality of impellers mounted to face each other on both ends of the rotary shaft. For convenience of explanation, the former may be classified as one side-type, and the latter may be classified as both end-type.

The one side-type turbo compressor may prevent a decrease in compression efficiency by shortening a pipeline or fluid passage connecting a plurality of impellers. However, in the case of the one side-type turbo compressor, the impellers on both sides may generate thrust in the same direction, and accordingly, axial turbulence increases, which may increase a size of a thrust bearing and making an overall size of the compressor too large. Also, as the load on a drive unit during high-speed operation increases, the drive unit may be overheated.

In the case of the both end-type turbo compressor, the impellers on both sides may generate thrust in opposite directions, and accordingly, axial turbulence may be prevented to a certain extent, which may decrease the size of the thrust bearing and enhancing motor efficiency. However, the both end-type turbo compressor requires a complicated and long pipeline or fluid passage to connect a plurality of impellers, which makes the compressor structure complicated and causes pressure loss in a process in which a fluid compressed by the impeller on one side moves to the impeller on the other side through a long flow path, thereby lowering compression efficiency.

U.S. Pat. No. 5,857,348 filed on Jan. 12, 1999 (hereinafter “Patent Document 1”) discloses an example of a both-end type turbo compressor. The both-end type turbo compressor disclosed in Patent Document 1 has a first impeller constituting a single-stage compression part (hereinafter, “first compression part”) on one side of a rotary shaft and a second impeller constituting a two-stage compression part (hereinafter, “second compression part”) on the other side of the rotary shaft, with an outlet of the first compression part and an inlet of the second compression part being connected by a communicating pipe.

The above both-end type turbo compressor has a radial bearing and an axial bearing on both ends or one end of the rotary shaft with respect to a drive unit. It is advantageous for a typical turbo compressor including the both-end type turbo compressor to quickly release motor heat generated from the drive unit by high-speed (for example, 40,000 rpm or above) rotation and frictional heat from a bearing supporting the rotary shaft, in terms of compression efficiency.

U.S. Pat. No. 8,931,304 filed on Jan. 13, 2015 (hereinafter Patent Document 2″) discloses a both-end type turbo compressor. In the both-end type turbo compressor disclosed in Patent Document 2, a refrigerant flow path is disclosed in which a refrigerant compressed in a single stage in the first compression part is directed into a motor chamber, and a drive motor and a bearing are cooled using the refrigerant compressed in a single stage and directed into the motor chamber and then drawn into the second compression part.

A turbo compressor having the above refrigerant flow path has a limitation in effectively cooling motor heat and frictional heat as a high-temperature refrigerant compressed in a single stage passes through the drive motor and the bearing. Also, the refrigerant, which is preheated as it passes through the motor chamber, is drawn into the second compression part, thus causing a volume loss due to an increase in specific volume of the refrigerant and leading to a decrease in compression efficiency.

Moreover, foil bearings are used in turbo compressors because they are suitable for the turbo compressors which rotate at high speed as stated above. Korean Unexamined Patent Application Publication No. 10-2004-0044115 published on Jun. 15, 2004 (hereinafter “Patent Document 3”)) discloses an example of an air foil bearing. The air foil bearing disclosed in Patent Document 3 has an air intake port on a sleeve supporting a plurality of air foils to supply air into gaps between a rotary shaft and the air foils.

The above air foil bearing (or gas foil bearing) is formed such that the air intake port radially overlaps the air foil bearings, and the air supplied through the air intake port may therefore come into direct contact with some of the plurality of air foils (for example, bump foils). This may cause a variation in bearing height between the air foils making direct contact with air and the air foils making indirect contact with air, leading to a change in pressure field between the rotary shaft and the bearing and making the rotation of the rotary shaft unstable.

Embodiments disclosed herein provide a turbo compressor capable of quickly releasing heat generated from a motor housing, and a refrigeration cycle device having a turbo compressor. Further, embodiments disclosed herein are directed to providing a turbo compressor capable of quickly releasing heat generated from a motor housing by supplying a refrigerant passed through a condenser directly into the motor housing, and a refrigeration cycle device having the same.

Furthermore, embodiments disclosed herein are directed to providing a turbo compressor capable of improving the effect of cooling a motor housing by supplying a refrigerant passed through a condenser directly into the motor housing and circulating it uniformly throughout the inside of the motor housing, and a refrigeration cycle device having a turbo compressor.

Embodiments disclosed herein provide a turbo compressor capable of stably supporting a rotary shaft that rotates at high speed using a gas foil bearing, and a refrigeration cycle device having a turbo compressor. Further, embodiments disclosed herein are directed to providing a turbo compressor that uses a gas foil bearing, capable of increasing rotational stability of a rotary shaft by keeping a bearing height of the gas foil bearing facing the rotary shaft constant, and a refrigeration cycle device having a turbo compressor. Furthermore, embodiments disclosed herein are directed to providing a turbo compressor that uses a gas foil bearing, capable of keeping the bearing height of the gas foil bearing constant by supplying a refrigerant as a working fluid at a uniform pressure along a circumference of the foil bearing, and a refrigeration cycle device having a turbo compressor.

Embodiments disclosed herein provide a turbo compressor capable of maximizing compressor performance based on load. Further, embodiments disclosed herein are directed to providing a turbo compressor that supplies refrigerant to a motor housing, capable of performing a load follow operation using a refrigerant passed through the motor housing, and a refrigeration cycle device having a turbo compressor. Furthermore, embodiments disclosed herein are directed to providing a turbo compressor capable of selectively supplying a refrigerant passed through a motor housing toward a first compression part or a second compression part, and a refrigeration cycle device having the same.

Embodiments disclosed herein provide a turbo compressor including a housing having a motor chamber; a drive motor having a stator and a rotor in the motor chamber of the housing; a first compression part and a second compression part respectively provided on opposite ends of the rotary shaft; a connecting passage portion connecting an exit of the first compression part and an entrance of the second compression part; an inlet passage portion penetrating one side of the housing to communicate with an inside of the motor chamber and guide a refrigeration fluid to the motor chamber; and an outlet passage portion penetrating the other side of the housing to communicate with the inside of the motor chamber and guide the refrigeration fluid in the motor chamber out of the housing. Thus, a gas foil bearing provided in the motor chamber may be quickly actuated by supplying a refrigeration fluid to the motor chamber, and at the same time, heat generated from the motor chamber may be quickly dissipated even in a high-speed operation, thereby improving efficiency of the turbo compressor and the refrigeration cycle device having the same.

For example, the motor chamber may include a first chamber provided on one (first) axial side with respect to the drive motor and a second chamber provided on the other (second) axial side, wherein an axial bearing is provided in the first chamber to support with respect to an axial direction of the rotary shaft, and the inlet passage portion communicates with the first chamber. Thus, the axial bearing may be quickly and uniformly actuated, and at the same time, the axial bearing and the rotary shaft may be quickly cooled.

More specifically, the axial bearing may be provided between an actuating support portion extending radially from the rotary shaft and a plurality of fixing support portions fixed to the housing and facing opposite axial sides of the actuating support portion, and at least a part or portion of the inlet passage portion may radially overlap some of the plurality of fixing support portions that are positioned between the actuating support portion and the first compression part. Thus, the refrigeration fluid may be quickly and uniformly supplied to the axial bearing, thereby quickly and uniformly securing bearing force and quickly cooling the axial bearing.

For another example, the motor chamber may include a first chamber provided on one (first) axial side with respect to the drive motor and facing the first compression part and a second chamber provided on the other (second) axial side and facing the second compression part, wherein the first chamber and the second chamber communicate with each other, and the outlet passage portion communicates with the second chamber. Thus, the refrigeration fluid, after cooling the axial bearing, may pass through the drive motor and be released, thereby cooling the entire motor chamber.

More specifically, the inlet passage portion may include: a first inlet passage portion communicating with the first chamber; and a second inlet passage portion communicating with the second chamber, wherein an axial support portion is provided in the first chamber to support with respect to an axial direction of the rotary shaft, and a refrigerant intake passage is formed in the axial support portion to allow the first inlet passage portion to communicate with the first chamber. Thus, the refrigerant introduced into the first chamber may be guided to a desired position, and at the same time, the refrigerant may pass through a member constituting the axial bearing, thereby quickly cooling the axial bearing.

For another example, an axial support portion may be provided in the motor chamber to support with respect to an axial direction of the rotary shaft, the axial support portion including a thrust runner radially extending from the rotary shaft; a first partition wall fixed to the housing and positioned between the thrust runner and the first compression part; and a second partition wall axially spaced apart from the first partition wall and fixed to the housing, that axially overlaps the thrust runner and is positioned between the thrust runner and the drive motor, wherein a refrigerant intake passage constituting the inlet passage portion is provided in the first partition wall, and an end of the refrigerant intake passage is open to a side of the first partition wall facing the thrust runner. Thus, a refrigerant constituting the refrigeration fluid may be quickly supplied to the axial bearing.

More specifically, an axial bearing may be provided between one (first) side of the thrust runner and the first partition wall and between the other (second) side of the thrust runner and the second partition wall, wherein the end of the refrigerant intake passage is positioned radially farther away from the rotary shaft than the axial bearing. Thus, when a refrigerant is supplied, the refrigerant is prevented from coming into direct contact with the axial bearing, and therefore the axial bearing may have uniform bearing force. Moreover, even if there is one refrigerant intake passage, the refrigerant may be uniformly supplied to a space where the axial bearing is installed.

Moreover, an axial bearing may be provided between one side of the thrust runner and the first partition wall and between the other side of the thrust runner and the second partition wall, wherein the end of the refrigerant intake passage is positioned radially closer to the rotary shaft than the axial bearing is. Thus, when a refrigerant is supplied, the refrigerant is prevented from coming into direct contact with the axial bearing, and therefore the axial bearing may have uniform bearing force. Moreover, a mass flow of refrigerant in a gap where the axial bearing is provided may be increased, thereby securing a bearing force more quickly and improving a cooling effect. This is particularly more advantageous when there is a plurality of refrigerant intake passages.

More specifically, the refrigerant intake passage may include a first intake passage open to a second side of the first partition wall, which is one of opposite axial sides thereof and faces the thrust runner; and a second intake passage open to a first side or inner circumferential surface of the first partition wall, which is one of the opposite axial sides thereof and is the opposite side of the second side. Thus, refrigerant may be quickly and uniformly supplied to a radial bearing as well as to the axial bearing.

Moreover, a refrigerant passage may be formed to radially penetrate the rotary shaft. Thus, refrigerant may move quickly over a wide area in a gap where the axial bearing is installed, thereby securing uniform bearing force and improving a cooling effect.

More specifically, the refrigerant passage may radially penetrate at least one of opposite axial sides, with the thrust runner interposed in between, and a cross-sectional area of the refrigerant passage may be larger than or equal to the distance between either side of the thrust runner and a partition wall facing the same. Thus, refrigerant may be smoothly introduced into a gap provided on opposite axial sides of the thrust runner, thereby securing more uniform bearing force and improving a cooling effect.

Further, the refrigerant passage may include a first refrigerant passage radially penetrating one (first) axial side and a second refrigerant passage radially penetrating the other (second) axial side, with the thrust runner interposed in between, wherein the first refrigerant passage and the second refrigerant passage communicate with each other by a third refrigerant passage which extends axially. Thus, refrigerant may move smoothly between gaps provided on opposite axial sides of the thrust runner, thereby securing more uniform bearing force and improving a cooling effect.

Additionally, a fourth refrigerant passage may be formed to radially penetrate the thrust runner. Thus, the thrust runner may be cooled more effectively.

Further, a first refrigerant passage or a second refrigerant passage may radially penetrate at least one of opposite axial sides, with the thrust runner interposed in between, wherein the fourth refrigerant passage communicates with the first refrigerant passage or/and the second refrigerant passage by a third refrigerant passage which axially extends. Thus, refrigerant may move more smoothly in a bearing receiving space where the axial bearing is provided, thereby securing more uniform bearing force and improving a cooling effect.

For another example, an axial support portion may be provided in the motor chamber to support with respect to an axial direction of the rotary shaft, the axial support portion including a thrust runner radially extending from the rotary shaft; a first bearing shell fixed to the housing and positioned between the thrust runner and the first compression part; and a second bearing shell axially spaced apart from the first bearing shell and fixed to the housing, that axially overlaps the thrust runner and is positioned between the thrust runner and the drive motor, wherein the first bearing shell includes an inner wall portion with a first shaft hole into which one end of the rotary shaft is rotatably inserted; a first side wall portion formed in the shape of a ring which radially extends from one (first) side of the outer circumferential surface of the inner wall portion; a second side wall portion formed in the shape of a ring which radially extends from the other (second) side of the outer circumferential surface of the inner wall portion; and a refrigerant receiving portion provided between the first side wall portion and the second side wall portion, with an inner peripheral side facing the rotary shaft and being blocked by the inner wall portion, and an outer peripheral side facing the inner circumferential surface of the housing and being at least partially open, wherein the inlet passage portion radially overlaps the refrigerant receiving portion. Thus, refrigerant may be spread through the refrigerant receiving portion of the first bearing shell, thereby quickly cooling the first bearing shell. Besides, it is easy to form a plurality of refrigerant passages, thereby reducing manufacturing costs and the cooling effects.

More specifically, a first radial bearing may be provided between the first shaft hole of the inner wall portion and the outer circumferential surface of the rotary shaft, and a refrigerant passage may be formed through at least either the inner wall portion or the first side wall portion to allow the refrigerant receiving portion to communicate with the motor chamber, wherein the refrigerant passage is open toward the motor chamber, in a position axially closer to the first compression part than the first radial bearing is. Thus, the height of the exit of the refrigerant passage may be reduced, and therefore the mass flow of refrigerant may be increased, thereby improving a bearing force and increasing a cooling effect.

Further, a first discharge sealing portion may be formed on an outer surface of the first side wall portion axially facing the first compression part, for sealing a gap between the first compression part and the first side wall portion, wherein the refrigerant passage is open so as to communicate with the motor chamber, in a position closer to the rotary shaft than the first discharge sealing portion is. Thus, the refrigerant passage may be positioned between the first discharge sealing portion and the first radial bearing, thereby smoothly supplying refrigerant to the first radial bearing.

Furthermore, a plurality of refrigerant passages may be formed at preset or predetermined intervals along a radius, and a passage cover may be provided on the outer surface of the first side wall portion axially facing the first compression part, for allowing open ends of the plurality of refrigerant passages to communicate with each other, wherein a passage connecting groove is formed on one side surface of the passage cover facing the first side wall portion to radially extend, for allowing the plurality of refrigerant passages to communicate with each other, and the passage connecting groove communicates with a shaft hole of the inner wall portion. Thus, large amounts of refrigerant may be supplied to the front of the first radial bearing, thereby increasing the bearing force of the first radial bearing provided in the first bearing shell and also increasing the cooling effect.

Furthermore, a first discharge sealing portion may be formed on the other side of the passage cover facing the first compression part, for sealing a gap between the first compression part and the first side wall portion. Thus, refrigerant is prevented from leaking to the motor chamber from the first compression part, thereby increasing compression efficiency and a bearing force of the bearing provided in the motor chamber and quickly cooling the bearing and the rotary shaft.

Moreover, a first axial bearing may be provided between the second side wall portion and the thrust runner, and a refrigerant passage may be formed through at least either the inner wall portion or the second side wall portion to allow the refrigerant receiving portion to communicate with the motor chamber, wherein the refrigerant passage is open, in a position radially closer to the outer circumferential surface of the rotary shaft than the first axial bearing is. Thus, a mass flow of refrigerant supplied to the first axial bearing may be increased, thereby increasing a bearing force of the first axial bearing and a cooling effect.

Additionally, a first intake passage may penetrate at least either the inner wall portion or the second side wall portion to allow the refrigerant receiving portion to communicate with the motor chamber, and a second intake passage may penetrate at least either the inner wall portion or the first side wall portion to allow the refrigerant receiving portion to communicate with the motor chamber. Thus, a refrigerant serving as a working fluid may be provided on one axial side of the first radial bearing, thereby increasing a bearing force of the first radial bearing and a cooling effect.

For another example, the turbo compressor may further include a second bearing shell fixed to the housing and positioned between the drive motor and the second compression part, wherein the second bearing shell has a second shaft hole into which the other end of the rotary shaft is rotatably inserted, and a refrigerant passage penetrating through the second shaft hole on a side of the second bearing shell facing the motor chamber. Thus, even if the gap between the second compression part and the second radial bearing is sealed, a refrigerant serving as a working fluid may be smoothly provided, thereby increasing a bearing force of the first radial bearing and a cooling effect.

For another example, the motor chamber may be divided into a first chamber and a second chamber on opposite axial sides, with the drive motor interposed in between, and the inlet passage portion may include: a first inlet passage portion communicating with the first chamber; and a second inlet passage portion communicating with the second chamber, wherein the first inlet passage portion and the second inlet passage portion communicate with the motor chamber on the same axial line. Thus, the first inlet passage portion and the second inlet passage portion may be easily connected to the housing, and at the same time, refrigerant may circulate over a great length in the motor chamber, thereby increasing a cooling effect of the motor chamber.

Further, the outlet passage portion may be positioned farthest away from the first inlet passage portion or the second inlet passage portion in a circumferential direction. Thus, refrigerant may circulate over a great length for a lengthy period of time in the motor chamber, thereby increasing a cooling effect.

Furthermore, the inner diameter of the first inlet passage portion may be larger than or equal to the inner diameter of the second inlet passage portion. Thus, more refrigerant may be supplied to the first chamber, and therefore the bearing provided in the first chamber may be more quickly actuated and quickly cooled.

For another example, the motor chamber may be divided into a first chamber and a second chamber on opposite axial sides, with the drive motor interposed in between, wherein an axial support portion is provided in the first chamber to support with respect to an axial direction of the rotary shaft, and the outlet passage portion communicates with the second chamber. Thus, a refrigerant introduced into the first chamber may circulate through the first chamber, thereby increasing the bearing force of the bearing provided in the first chamber and at the same time increasing the effect of cooling the bearing provided in the first chamber and the rotary shaft.

Further, the outlet passage portion may include a first connecting passage having one (first) end communicating with the second chamber, and another (second) end communicating with the connecting passage portion; a second connecting passage having one (first) end communicating with the connecting passage portion, and another (second) end communicating with an entrance of the first compression part; and a refrigerant control valve for controlling the flow of a refrigerant passed through the motor chamber to be directed toward the first connecting passage or the second connecting passage. Thus, a refrigerant passed through the motor chamber may be properly guided to the first compression part or the second compression part according to an operation mode of the compressor, thereby maximizing compression efficiency.

Furthermore, the refrigerant control valve may further include a valve control portion for controlling opening/closing directions according to preset or predetermined conditions, wherein the valve control portion allows the second chamber to communicate with the entrance of the second compression part under a high-load condition, and allows the second chamber to communicate with the entrance of the first compression part under a low-load condition. Thus, the enthalpy of refrigerant supplied to the second compression part may be lowered under the high-load condition to increase compression efficiency, whereas a temperature of refrigerant supplied to the first compression part may be raised under a low-load condition to lower a cooling force.

Embodiments disclosed herein further provide a refrigeration cycle device including a compressor; a condenser connected to a discharge side of the compressor; an expander connected to an exit of the condenser; and an evaporator having an entrance connected to an exit of the expander, and an exit connected to an intake side of the compressor, wherein the compressor includes the above-described turbo compressor. Thus, the turbo compressor may quickly and uniformly secure bearing force for each bearing by using a gas foil bearing, thereby stably supporting the rotary shaft. At the same time, the turbo compressor may perform a load-dependent operation properly according to an operating condition of the refrigeration cycle device, thereby improving efficiency of the refrigeration cycle device including the turbo compressor.

More specifically, the inlet passage portion may be connected between the exit of the condenser and an entrance of the expander. Thus, the refrigerant of the refrigeration cycle device may be used, and the turbo compressor and the refrigeration cycle device having the same may be operated effectively and cooled.

A turbo compressor and a refrigeration cycle device having the same according to embodiments disclosed herein may include an inlet passage portion penetrating one (first) side of the housing to communicate with an inside of the motor chamber and guide a refrigeration fluid to the motor chamber; and an outlet passage portion penetrating the other (second) side of the housing to communicate with the inside of the motor chamber and guide the refrigeration fluid in the motor chamber out of the housing. Thus, a gas foil bearing provided in the motor chamber may be quickly actuated by supplying a refrigeration fluid to the motor chamber, and at the same time, heat generated from the motor chamber may be quickly dissipated even in a high-speed operation, thereby improving efficiency of the turbo compressor and the refrigeration cycle device having the same.